Asphaltic composite monolithic shield



Jan. 22, 1957 L. F. BRAMBLE ASPHALTIC COMPOSITE MONOLITHIC SHIELD FiledSept. 8, 1955 United States Patent O ASPHALTIC COMPOSITE MoNoLITHIcSHIELD Lloyd F. Bramble, Houston, Tex., assgnor to Gulf States AsphaltCompany, Inc., Houston, Tex., a corporation of Texas ApplicationSeptember 8, 1955, Serial No. 533,136

3 Claims. (Cl. 154-41) This invention relates to new and usefulimprovements in rock shields, and particularly to a new asphalticcomposition employed in the manufacture thereof, and to a new method ofapplying the rock shield to a pipe line.

The prior art shows that it is old to employ rock shields for protectingpipe and the coating on said pipe when the pipe is being laid in rockyareas; to shield a coated pipe at river crossings; to shield a coatedpipe when dragging or pulling the pipe through swamps; and to shield acoated pipe whenever and wherever the pipe an-d its coating are subjectto rough handling.

The prior art shows also, that it is old to attach rock shields to apipe by wrapping the shield or membrane entirely around the pipe afterthe. fashion of applying a cigarette paper to a quantity of tobacco. Theshield or membrane is subsequently fastened to the pipe by the use ofwire or metal bands. The prior art shows also that the shield ormembrane may be applied to the pipe by spirally wrapping the same aboutthe pipe, and by using many lobvious methods and means of fastening theshield in place.

The present invention relates particularly to a rock shield that isadapted to protect gas and oil pipe lines, the pipe cross-sections ofwhich frequently range in diameters between twelve and thirty inches,the pipe lines being laid in rough rocky terrain; across swamps andrivers; under highways and railroads; and in fact under many dicultinstallation conditions. The pipe line must be protected against damageby rocks when backlling takes place; and any coatings that might havebeen applied to said pipe line must also be protected from such damage.The function of the rock shield is to resist penetration of rocks orother foreign matter held under constant pressure of the backfill in aditch after the pipe has been laid.

The present invention is directed to a new asphaltic composition ormaterial employed in the manufacture of the shield and also to a newmethod of applying that asphalt composition or material to a pipe line.

It is therefore an object of this invention to provide afrock shield forpipe lines wherein the shield is substantially non-shrinking,non-curling, non-cracking, and is readily curved without cracking evenin large strips or sheets, and is capable of withstanding the weight andsustained pressure of back-fill material such as rocks and dirt withoutpuncturing or cutting action developing.

An important object of this invention is to provide a rock shield havinga' central asphaltic composition or mastic layer consisting essentiallyof asphalt and sand in specified proportions; asphalt comprising fromfifteen (l5) percent to forty (40) percent of the composition and sandcomprising from sixty (60) percent to eightyve (85) percent of thecomposition. The important characteristics are both the particle sizeand particle shape of the sand used, and the asphalt used, whereby theoptimum factors of resistance to pressure and resistance to impact ofrocks and other damaging things are developed.l

A further object of the invention relates to a method 2,778,406 PatentedJan. 22, 1957 ICC of applying the asphalt material and the shield to apipe line, during the period of installation of the pipe line.

The invention will be more readily understood from a reading of thefollowing specification and by reference to the accompanying drawingforming a part thereof, and wherein:

Figure l is a sectional view showing a ditch or trench in which a pipeis being laid with the rock shield in place on said pipe;

Figure 2 is an enlarged sectional view'of the shield and pipe taken online 2-2 of Figure 1; and

Figure 3 is an isometric view of the testing device known as a blunt rodpenetrometer employed in testing samples of the rock shield.

In the drawings, 10 represents the outlines of a trench or ditch whichhas been prepared in terrain traversed by la gas or oil pipe line. Theterrain may be swampy or dry; and it may be largely composed of `dirtand rocks, or it may be composed principally of rocks. The manner ofpreparing the trench forms no part of this invention. The pipe 11, shownin section consists of the usual lengths of steel pipe su-ch as isemployed in pipe lines, welded together at abutting sections and varyingin diameters between twelve and thirty inches. The manner of fabricatingthe pipe line forms no part of this invention, and as shown in thedrawing the trench has been made, the pipe line has been laid in thetrench and the rocks and dirt previously excavated are to be back-filledinto the trench to partially or entirely iill the trench and cover upthe pipe line. Such back-filling operation is customarily effected bymeans of mechanically actuated bulldozers or other suitable filling andgrading machines and rocks and dirt are literally showered or dumpedupon the pipe line, developing impacts from the rocks upon the surfaceof the pipe and adding accumulating pressures to the pipe as the rocksand dirt are filled in, thus causing great abuse to the surface of thepipe or to the material encasing or shielding sai-d pipe.

As shown in Figure 1, the shield 12 is placed only upon the exposed areaof the pipe 11, ,that is, the area most likely to be damaged in theback-lling proeess.- The shield 12 will be described hereinafter but forthe purposes of Figure 1 it is suicient to state that the shield ismanufactured in lengths `of six to twelve feet and of widths ofseventeen to thirty inches for pipe sizes four to eight, land in lengthsof three feet and of widths of thirtyeight to fty inches for pipe sizesten to thirty-six. The shield is preferably placed upon the pipe asshown in Figure l, and this is sufficient, but a shield may becompletely wrapped around the pipe if that is deemed necessary. Theshield is readily curved about the exposed surface of the pipe 11 andsecured to the pipe in a mauner hereinafter described.

The shield of this invention, as shown in section'at A in Figure 2,includes a central asphaltic composition lmastic layer 13 which isdisposed between outer layers Percent Asphalt 15 to 40 Sand 60 to 85 Theasphalt employed in the mastic has the following characteristics:

Melting point, ball and ring l00-230 F. Penetration at 77i2 F 5-100arranca but it has been determined in (tests that a typical physicalcharacteristics analysis of the asphalt employed, approaching that ofthe most desirable, is as follows:

4Melting point, ball and ring l'75230 F. Penetration at 77i2 F 5-35 Theasphalt preferably is of the catalytically blown asphalt type, such asdisclosed in the patent to Hoiberg, 2,450,756, 'but air blown andnatural asphalt may be utilized.

The sand employed in the `mastic must be at least 94%i silica; of 95%30-80 mesh, with no particle size larger than 30 mesh and having aKrumbein number ranging from 0.3 to 0.7. The sand particles may beroughly fovoid, oblong, spheroid, rectangular or any shape ranging fromsquare to round but having definite edges and being crysalline innature. The Krumbein number is a technical notation made concerning theshapes of crystalline materials, and indicates the shape ranging fromsquare to round, and numbered from 0.1 (square) to v1.0 (round).

The asphalt composition mastic differs from the prior art masticsincluding asphalt and llers and fibers with or without roofing materialscrap, in that it includes a sand the particle size and shape of whichare important, and the asphalt in the predetermined percentages. Thiscomposition mastic develops the optimum resistance to pressure as wellas to impact of falling rocks.

The shield, in the process of manufacture, may be coated with acontinuous coat of asphalt having the above typical analysis, and thisprevents the penetration or absorption of moisture or moisture vaporwhich, if not prevented, would accelerate the tendency of theunprotected surfaces of rag felt, asbestos felt, kraft paper and thelike to shrink. This tendency to shrink is very marked; sometimesamounting to as much as fifty percent of the surface area; and isparticularly noted when the surface area is subjected to above-groundweathering. Unless corrected, the shrinkage in surface areas of rockshields placed upon a coated pipe would normally have a very high stresseffect upon the coating which is supposed to be protected. Thus, byavoiding the shrinking factor in the manner above noted, the originallineal dimensions of the shield are maintained, and this is a veryimportant factor to be considered in protecting pipes and theircoatings, during their life expectancy.

The rock shield is preferably formed by continuously moulding the layers14 and 15 into contact with the composition mastic layer 13 when it ishot and in a semisolid form. This permits the ow of the masticcomposition into the adjacent surfaces of the layers 14 and 15 wherebythe layers are united adhesively with the mastic composition layer.Hence the resulting sheet, after being coated with the asphalt asdescribed above, is non-cracking, resistant to pressure and impacts,noncurling and non-shrinking.

The method of attaching the rock shield 12 consists in employing eithera hot or cold application of the asphalt, described above, which may beapplied to the pipe 11, and is shown at 16 in Figure 2. The asphalt maybe applied over the surface of the pipe to be covered by the shield, or,preferably, in spaced spots, so that the asphalt serves the sole purposeof holding the shield in place on the pipe until the ditch or trench hasbeen covered or back-filled. This method of attaching the shield to thepipe eliminates the costly prior art practice of employing metal wiresor straps.

In the course of development of the rock shield forming a part of thisinvention, a special testing equipment, shown in Figure 3, but one notinvented by the applicant, was employed for checking blunt rodpenetration and cold flow characteristics of samples of the shieldforming a part of this invention. It has been termed, by those skilledin this art, a blunt rod penetrometer.

As shown at 20 and 21 two samples of the shield, as made in accordancewith the above disclosure, are being tested. All tests in a wellconducted laboratory are run, either in duplicate or in triplicate, inorder to avoid any misinterpretation of results. A series of tests andseveral pieces of apparatus such as shown in Figure 3 are set up to showcomparative .penetration of the blunt rod over a period of time.

in Figure 3, the Vsamples 2d and 21 are placed upon a part 'of the framemember 22 which is constructed in the manner shown. A pair of vfree-rnoving 1A: inch rods are placed in a vertical position as shown, saidrods contacting samples 20 and 21 as shown. The upper ends of the rodsare provided with cups 24, 24 adapted to receive varying quantitiesoflead shot. Beneath each cup and spaced therefrom are washers 25, 2S,through which the rods 23, 23 extend but are secured to the washers.Each washer' is spaced the same distance clownwardly from its respectivecup. Arranged parallel to each rod 23, 23, is a second Mt inch rod 26attached to the frame 22 and extending vertically beneath the washer 25.Each rod 26 is of the same length and is spaced the sarne distancedownwardly from each washer 25. Hence, before the samples 20 and 21 areplaced in the penetrometer, each set of parts 23, 24, 25, and 26 hasidentical characteristics.

The blunt rods 23, 23, are so constructed so as to move freely up anddown in the frame member 22, and each rod is 1A inch in diameter andapproximately l0 inches long. A total load on each rod is placed at therate of ten pounds per square inch of bearing surface. Afcr havingplaced the blunt rod on the material 20, I21, a preliminary reading istaken with an inside caliper vto the -closest micron. Daily readings aretaken and yrcicordcd, the test being carried out at a temperatureof 77"12 F.

The purpose of the washers 25, which are xedto the blunt rods 23, 23, islto furnish a surface upon which one leg of a caliper is placed inyorder to measure the distance which the rods drop over any specifiedperiod of time, due to the blunt rods having penetrated the samples 20,and 21. The purpose of the stationary vertical rods 26, -26 is to form asurface on which the other leg of the caliper is placed when taking apenetration measurement. The depth `of the penetration of the rod ismeasured over a period of time and recorded for Various materials,samples, or comparative materials.

It can thus be seen that a shield has been provided which has all of thedesirable properties necessary for a rock shield, and the particularconstruction thereof eliminates the disadvantages of the prior art. Ininstallation and use, the invention will very markedly decrease both thecost of material required for pipe protection and the cost `of labor ofinstallation in that the strapping and fastening devices needed `tohandle the shield in the normal conventional ways have been avoided.

It should bepointed out that the penetration characteristics ,given`previously herein and those recitedinpthe claims for ythe variousasphalts were determined with standard tests and equipment and not with`the test-apparatus of Fig. 3. Such apparatus of Fig. 3 is used to testthe final laminatedproduct `or shield A (Fig. l2) todetermine itsrelative resistance to impact by rock-s andthe like as compared to othermaterials which have been proposed and/ or used for rock shields.

What is claimed is: l

l. An asphaltic composite monolithic shield for use in covering pipelines, comprising an intermediate asphaltsand composition layer havingan upper and a lov/er surface, a layerof fibrous reinforcing material oneach of Isaid surfaces of said asphalt-sand composition layer, andbonded thereto to form a composite monolithic sheet, said sheet having athin Aouter coat of waterproof asphalt thereon rendering saidreinforcing material impervious to moisture for preventing the shrinkingthereofy and 'said asphalt-sand composition layer consisting essentiallyof asphalt in the amount of 15% to 40% and sand in the amount of 60% to85%, the asphalt in said composition layer having a melting point (ba-11'andi-ing) in the range of 175 F.230 F. and a penetration at 77 F. offrom 5-35, whereby -said shield is substantially non-curling,non-cracking, non-shrinking and resistant to impacts.

2. An asphaltic product as set forth in clairn 1, wherein the asphalt insaid waterproof asphalt coating has a melting point (ball and ring) inthe range of 100 F.230 F. and a penetration at 77 F. of from 5-35.

3. An asphaltic product as set forth in claim 1, wherein the sand insaid asphalt-sand composition -layer is at least References Cited in thele of this patent UNITED STATES PATENTS OTHER REFERENCES Book entitledAsphalts and Allied Substances, by Abraham, 5th ed., vol. 2 (Methods ofTesting). D. Van Norstrand Publisher, pages 989 and 990 of interest.

